Potential Dangers of Simplifying Combined Sewer Hydrologic/Hydraulic Models
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VIEW THE REPLYPublication: Journal of Hydrologic Engineering
Volume 14, Issue 6
Abstract
In large combined- and storm-sewer systems it is impractical to model every pipe, manhole, and component of the system. Time and budget constraints, combined with a lack of relevant input data, compel modelers to make assumptions in a quest to create a simplified model that adequately represents the hydrologic and hydraulic behavior of the system. Two of the most commonly applied simplification techniques are conduit skeletonization and subcatchment aggregation. This paper aims to highlight the potential dangers of making such simplifications, allowing modelers to make qualified simplifying assumptions. A base model and four simplified models were tested for a small catchment in Chicago using the simulation packages ILLUDAS, HEC-HMS, and InfoSWMM. In addition, a base model and five simplified models were compared for a catchment using InfoSWMM. The effects of conduit skeletonization and subcatchment aggregation were found to be dependent on the simulation package being used and sensitive to the degree of simplification of the system. In using simplified models there is a danger that the user may not correctly predict the magnitude, timing, and shape of the outfall hydrograph.
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Acknowledgments
This research would not have been possible without ongoing funding and support from the Metropolitan Water Reclamation District of Greater Chicago as part of the University’s work on Chicago’s Tunnel and Reservoir Plan.
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Information
Published In
Journal of Hydrologic Engineering
Volume 14 • Issue 6 • June 2009
Pages: 596 - 605
Copyright
© 2009 ASCE.
History
Received: Mar 31, 2008
Accepted: Sep 5, 2008
Published online: Feb 20, 2009
Published in print: Jun 2009
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